Since new applications and upcoming standards require increasing data rates and lower power consumption, the study and development of new architectures of communication transmitters for user units is very active. The in-phase and quadrature modulator (IQ modulator) is a key component in modern wireless transmitters. I-Q up conversion is one of the architectures of choice for implementing transmitter signal chains for end applications such as cellular, WiMAX, and wireless point-to-point. It provides a convenient method for modulating data bits or symbols onto an RF carrier.
In a typical wireless transmitter that uses I-Q modulation, an input data comprises an in-phase component and a quadrature component. The I-Q transmitter comprises a DAC, for example an RFDAC that convert the in-phase and the quadrature components to a pair of I and Q output signals. RFDACs directly convert a digital baseband signal into an RF output signal, by using a building block which combines digital-to-analog conversion and up conversion mixing. High-performance digital-to-analog converters with high resolution can provide the flexibility needed to support multiple frequency bands and multiple standards in modern wireless communication transmitters. For cellular applications such as WCDMA or LTE, the required resolution of DACs is typically in the range of 15 bits. However, the high resolution DACs lead to higher power dissipation.